Spamsnake - Mail Transport Unavailable Issue

[frogman]

I believe I have followed The Perfect SpamSnake - Ubuntu Jaunty Jackalope -Howto to the letter...

I am down to what I hope is my final challenge:

Incoming messages are getting stuck after content scanning in the postfix queue. When forcing a flush on the queue, I get the following in the log:

Oct 25 17:16:55 spamsnake postfix/qmgr[4015]: 12361BE9BB: from=<sender@domain.tld>, size=2853, nrcpt=1 (queue active)
Oct 25 17:16:55 spamsnake postfix/qmgr[4015]: warning: connect to transport SMTP: No such file or directory
Oct 25 17:16:55 spamsnake postfix/error[4439]: 12361BE9BB: to=<user@transportdomain.tld>, relay=none, delay=8858, delays=8858/0.03/0/0.02, dsn=4.3.0, status=deferred (mail transport unavailable)

transportdomain.tld refers to a single transport domain that I have defined.

Is anyone else experiencing this issue? Any thoughts?